MOLECULAR MECHANICS AND QUANTUM CHEMISTRY EVALUATION OF THE EFFECT OF THE SIDE CHAIN STRUCTURE OF BRASSINOSTEROIDS ON THEIR BIOLOGICAL ACTIVITY
V. M. Andrianov1, I. V. Anishchenko2
1Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk, Belarus
2United Institute of Informatics Problems, National Academy of Sciences of Belarus, Minsk, Belarus
Keywords: brassinosteroids, brassinolides, conformers, biological activity, conformational analysis, side chain, hydrogen bond
Abstract
Using methods of molecular mechanics and quantum chemistry in the DFT approximation, a conformational analysis of one of the most biologically active compounds of the class of brassinosteroids, natural brassinolide, and less active natural 24-epibrassinolide and synthetic (22S,23S)-24-epibrassinolide is performed with a subsequent comparison of their side chain structures. Found that the 22R,23R,24S-configuration of two hydroxyl and one methyl groups of brassinolide provides the side chain structures in which its diol system forms an O6…H(O5) intramolecular hydrogen bond. Therewith, the O6H hydroxyl group is free and can participate in the formation of intermolecular hydrogen bonds with a receptor. On the contrary, the 22S,23S,24R-configuration of (22S,23S)-24-epibrassinolide corresponds to the side chain structures in which the O6H hydroxyl group is shielded by the 21-methyl group, which determines a lower biological activity of this hormone.
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